Maximal exercise capacity in chronic obstructive pulmonary disease: a limited indicator of the health status

Dyspnoea and diminished functional status are pivotal features of the health status (HS) in chronic obstructive pulmonary disease (COPD). However, it is still not fully understood how pulmonary function tests and cardiopulmonary exercise testing relate to these aspects. This may be due to incomplete assessment and/or deficient definitions of HS. Especially regarding peak oxygen consumption, inconsistent results have been reported.

To determine the value of maximal cycle ergometry in relation to a broad spectrum of HS aspects.

129 patients with COPD, stage II and III according to the GOLD classification, performed a cardiopulmonary exercise test. Sixteen independent sub-domains of HS were assessed according to the Nijmegen Integral Assessment Framework, covering physiological functioning, complaints, functional impairments and quality of life as main domains. VO(2)(max) and HS sub-domains were correlated by bivariate analysis.

Weak correlations of VO(2)(max) with most sub-domains were found, except for exercise capacity; the other 5 sub-domains of physiological functioning did not correlate. Between different types of exercise limitation (5 types were differentiated), no significant differences were noted in the scores of 13/16 HS sub-domains.

VO(2)(max) is indeed correlated with most aspects of HS, except for physiological variables, but associations are weak. No single exercise limitation type is associated with specific HS problems. Thus separate assessment of all HS sub-domains is advocated to ensure adequate planning of therapeutic interventions.